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25 lines
1012 B
25 lines
1012 B
3 years ago
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# 一些写代码的技巧
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## 如何获知变量类型或者函数的返回类型
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有几种常用的方式:
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- 第一种是查询标准库或者三方库文档，搜索`File`，然后找到它的`open`方法，但是此处更推荐第二种方法:
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- 在[Rust IDE]章节，我们推荐了`VSCode` IED和`rust-analyze`插件，如果你成功安装的话，那么就可以在`VScode`中很方便的通过代码跳转的方式查看代码，同时`rust-analyze`插件还会对代码中的类型进行标注，非常方便好用！
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- 你还可以尝试故意标记一个错误的类型，然后让编译器告诉你:
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```rust
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let f: u32 = File::open("hello.txt");
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```
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错误提示如下：
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```console
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error[E0308]: mismatched types
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--> src/main.rs:4:18
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4 | let f: u32 = File::open("hello.txt");
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| ^^^^^^^^^^^^^^^^^^^^^^^ expected u32, found enum
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`std::result::Result`
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= note: expected type `u32`
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found type `std::result::Result<std::fs::File, std::io::Error>`
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```
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